NATURAL HISTORY OF SELBORNE 185 



LETTER XXXIX 



SELBORNE, May i^th, 1778. 



DEAR SIR, Among the many singularities attending those 

 amusing birds the swifts, I am now confirmed in the opinion 

 that we have every year the same number of pairs invariably ; 

 at least the result of my inquiry has been exactly the same for 

 a long time past. The swallows and martins are so numerous, 

 and so widely distributed over the village, that it is hardly pos- 

 sible to recount them ; while the swifts, though they do not 

 build in the church, yet so frequently haunt it, and play and 

 rendezvous round it, that they are easily enumerated. The 

 number that I constantly find are eight pairs ; about half of 

 which reside in the church, and the rest build in some of the 

 lowest and meanest thatched cottages. Now as these eight 

 pairs, allowance being made for accidents, breed yearly eight 

 pairs more, what becomes annually of this increase, and what 

 determines every spring which pairs shall visit us and reoc- 

 cupy their ancient haunts ? 



Ever since I have attended to the subject of ornithology, I 

 have always supposed that that sudden reverse of affection, 

 that strange avrio-Topyrj, which immediately succeeds in the 

 feathered kind to the most passionate fondness, is the occa- 

 sion of an equal dispersion of birds over the face of the earth. 

 Without this provision one favorite district would be crowded 

 with inhabitants, while others would be destitute and forsaken. 

 But the parent birds seem to maintain a jealous superiority, and 

 to oblige the young to seek for new abodes ; and the rivalry 

 of the males in many kinds prevents their crowding the one on 

 the other. Whether the swallows and house-martins return in 

 the same exact number annually is not easy to say, for reasons 

 given above ; but it is apparent, as I have remarked before in 

 my monographies, that the numbers returning bear no man- 

 ner of proportion to the numbers retiring. 



